This invention relates generally to multistation systems for performing diverse operations on products and more particularly to the configuring, automation and control of such a multiple station facility. For purposes of explanation, the invention is described herein in the context of testing and/or repairing printed circuit boards but it should be understood that the principles of the invention are also applicable to these and other operations performed on other products. (The term printed circuit board as used herein refers generically to electrical circuits which are constructed on or within supporting strata. The use of this term is not intended to limit this invention to electrical circuits having conductive members formed by "printing" techniques nor to circuits formed on or within a supporting stratus of any specific construction).
In order to test such printed circuit boards (PCBs) it is necessary to establish electrical connection between the test equipment and selected nodes within the electrical circuits of the PCB. Conventionally this electrical connection is accomplished with a fixture assembly upon which the PCB is positioned. The fixture assembly incorporates a plurality of conductive probes (traditionally referred to as a bed of nails) which are selectively positioned therein to correspond to predetermined electrical nodes on the PCB. After the PCB is positioned upon the fixture assembly the probes are biased into electrical contact with such nodes. The various probes of the fixture assembly are in turn electrically connected to stimulus and measurement means within the test equipment which stimulate the nodes and which measure the responses which occur at the nodes of the PCB under test as a result of such stimulus. A separate fixture assembly is generally required for each different PCB to be tested due to the variation of the circuits of the PCB and of the electrical nodes located therein. Since the electrical connection between the electrical nodes of the PCB and the test system is very critical, since the trend is to design PCBs with electrical nodes which are very densely packed, and since there is such a variation in the size and configuration of the different PCBs, the accurate loading or positioning of a PCB with respect to the fixture assembly and the accurate loading and positioning of the fixture assembly as well as the electrical connection of the fixture assembly to the stimulus and measurement means of the test equipment have typically been manual processes which make up an excessively large proportion of the total test time. Attempts to automate such processes through the use of robotic arms or univeral fixtures have been limited due to the required accuracy, the inherent variability in the size, shape, complexity, and fragility of PCBs, and the associated cost and complexity of the robotic arms and the universal fixtures. Once a robotic arm is programmed it is also extremely difficult to alter the configuration of the operating modules between which the robotic arm is tasked to repetitively perform. Furthermore, neither the robotic arms nor the universal fixtures have achieved much success with reducing the amount of time required to load and position the fixture assembly, load and position the PCB with respect to the fixture assembly, make the electrical connection with the PCB, remove the PCB from the fixture assembly, and prepare the test equipment for testing the next PCB (especially if the next PCB has a different configuration). These concerns are compounded when multiple test and/or repair stations are employed in a test system